Industrial facilities, such as factories, warehouses, garages, and the like use rollup doors to cover doorways or to guard machinery in order to provide security, as well as protection from debris, and unwanted climatic variations. Typically, an industrial rollup door with rollable door leaf includes rail frame components on the left and right sides of the doorway and a door leaf comprised of a plurality of lamellae or panels adapted to travel within the left and right frame components. In one particular type of door, a lifting component is attached to the door and to a rotary shaft mounted above the doorway, when the door is made for a vertical installation. To operate the door, the rotary shaft is activated in one direction to roll the door leaf up onto the shaft to open the doorway. Rotation in the opposite direction unrolls the door leaf to close the doorway. Vertical operation is typical, but angled operation is also possible.
Typical industrial rollup doors had a number of drawbacks in their operation. It was recognized, for instance, that substantially rigid flat lamellae had desirable characteristics, such as providing a secure barrier, but could not be rolled up in a compact fashion. The initial layer of lamellae would not conform to the curvature of the rotary shaft because of the rigidity of the lamellae. Because the leaf would not conform to the curvature of the rotatable shaft, the rolled up door leaf would assume an asymmetrical configuration with significant gaps between the leaf and the shaft. The rigid leaf assumed a tangential orientation with the shaft. Additional layers could not conform to the underlying layers, creating additional gaps. The retracted door in an end view when wound on the shaft, assumed an asymmetric polygonal shape, rather than a closely packed, symmetric and smooth circular shape. Furthermore, additional layers wound on the shaft rested upon the inadequately supported prior layers, subjecting the prior layers to significant bending loads and leading to damage.
Related drawbacks include the noise and wear resulting from contact between subsequent layers of the lamellae. Layers of lamellae coming in contact with each other as the door is operated, either up or down, generate undesirable noise. In addition to noise, contact between lamellae created wear on the contacting surfaces which is manifested by aesthetically objectionable marks. Continued wear could result in damage to the integrity of the door.
One innovation that addressed the noise and damage concerns is presented in U.S. Pat. No. 6,883,577 (“the '577 patent”). The '577 patent provides door leaf or lamellae of increasing width from the top of the doorway to the bottom with guidance provided by side rails or frames located at the edges of the doorway. A rotating shaft is fitted with spiral surfaces of increasing diameter from a central portion of the shaft toward the outward ends of the shaft. Overall the outer surface shape is that of a stepped cone. As the shaft rotates to lift the door, the narrower door leaf is taken up first by the inwardly located conical surfaces. Subsequently wider door leaf is taken up by the appropriately located conical surfaces of greater diameter located closer to the ends of the shaft. Dampening material is located on the rotating surfaces to attenuate noise generated by contact between the round surfaces and the lamellae. The conical surfaces are configured to maintain spacing between successive layers of lamellae, thereby preventing noise and damage caused by contact.
The prior art cited effectively addressed the noise and damage issues but has other characteristics for which improvement may be desired. In order to properly guide and control the left and right ends of the rollup door, the side frames provided must be sized to guide the narrowest lamella as well as the widest. To accommodate both the narrowest and the widest lamellae, the side frame either was tapered from a deeper rail at the top of the doorway to a less deep shape at the bottom, or the rail was made uniformly deep enough to guide the narrowest lamellae. Such side rails are somewhat expensive to manufacture or somewhat decrease the available doorway width, or both. Additionally, the complexity of the rotating shaft increased to a certain degree the production cost and weight of the shaft, and increased the size of the required motor to drive the shaft. Further, the lamellae of the prior art door are, by necessity, of various lengths. This requires an inventory of various lengths of lamellae for replacement purposes.
U.S. Pat. No. 5,307,859 (“the '859 patent”) teaches an alternate industrial rollup door in which a doorway is covered by a flexible transparent sheet or curtain suitable for winding onto a shaft to open a doorway or unwinding from the shaft to block the doorway. Horizontal stiffening members are provided at various vertical locations to provide stability. According to the invention, two strips of sufficient thickness are formed on the curtain so that each of them is rolled onto itself while the curtain is being raised. When the curtain is rolled up, contact between front and back faces of the curtain is limited, and no contact occurs in the vicinity of the strips. The separation preserves the transparency of the curtain over time. Although transparency may be desirable in certain applications, flexible sheet or curtain doors do not provide significant resistance to breaching.
The present invention addresses the shortcomings of the prior art by providing a rollup door that can be wound up in a compact way at a high speed, generating less noise and less wear, while also protecting the lamellae from damage during operation.